Abstract
During tunneling in loose grounds, the ground deformation caused by drillings around the tunnel, leads to land subsidence and the adjacent tunnel which would affect tunnel structure and surrounding structures. In such situations it is necessary to improve the properties of the ground prior to drilling operations. In order to acquire tunnel face stability during excavation operations in areas with loose soil fault or areas with lack of adhesion, there are various methods such as split cross drilling, frame holder or auxiliary pre-holding methods such as umbrella arch method; pre-holding methods must provide safety when drilling and must be affordable, economically. In this study, we assessed the previous studies on methods and behaviors of umbrella arch strategy in reinforcing the concrete tunnels, reached the purpose with experimental and numerical methods and offered the latest design achievements, implementation progresses and analysis in relation with this method.
Highlights
Umbrella Arch Method (UAM) or Forepole is a conventional and economical method in tunnel excavation, and is in use to increase the excavation front sustainability, minimize the land subsidence, and prevent debris rocksHow to cite this paper: Rostami, A., Dehkordi, P.K., Ziarati, M.A., Jahani, S. and Lotfi, K. (2016) The Types of Tunnels Maintenance in Umbrella Arch Method
Pipe roof method is another method in pre-arming tunnels, which is done with installing large diameter steel pipes, around the drilling front
By examining 24 projects in which the procedure was reinforcing the tunnel face excavation by umbrella method, it was found that the main reason for the application of umbrella arch in 55% of cases is increasing the stability of the front drilling, and in 36% of cases is lowering the land subsidence as the primary goal of using this method
Summary
Umbrella Arch Method (UAM) or Forepole is a conventional and economical method in tunnel excavation, and is in use to increase the excavation front sustainability, minimize the land subsidence, and prevent debris rocks. In this strategy at first some holes will be drilled in a semi-circular pattern at a high point of the tunnel and around the tunnel crown. The main advantages of this method can be: stress reduction in drilling front, safety increase during drilling operations, simplicity of drilling operations and as a result increase in the drilling progress speed. Umbrella approach was first used in the early sixties in Belgium, for the construction of the subway station of Antwerp This method was extensively used in America and in Japan to build tunnels with small diameters and to dig subway stations [2].
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